1. Field of the Invention
The present invention relates to an apparatus for calculating a photographing field angle using three-dimensional information (distance image and the like) of photography space.
2. Description of the Related Art
In the field of computer vision, three-dimensional shape recognition of an object disposed in a photography space or depth recognition of the photography space is often practiced by optically measuring the positions of points visually recognizable when the photography space is observed from a certain direction. As for the measuring method, the following are known: stereo image method that employs principles of trigonometry, TOF (time of flight) method that measures a time from irradiation of light to receipt of reflected light, light section method that examines pattern light when slit light is irradiated, and the like.
An image produced by representing the positions of visually recognizable points as coordinates of a predetermined coordinate system and recording the coordinate values as pixel values is generally referred to as “distance image” or “depth image”. The distance image includes spatial position information recognized by humans by observing a target with both eyes. In the mean time, RGB data or a gradation image obtained by ordinary photography includes color and brightness information recognized by a human when observing an object. Accordingly, combination of information obtained from the distance image and information obtained from the RGB data or the like may cause a computer to recognize information substantially identical to that obtained by human vision. This allows a stereoscopic image in a photography space to be reproduced on a monitor or to cause a computer to recognize a three-dimensional object.
Such technologies are useful in every industrial field and many studies have been carried out as described, for example, in U.S. Patent Application Publication No. 20020030675.
Image processing using a distance image may sometimes require photographing field angle information. For this purpose, it is often the case that, when a photograph operation is performed and a distance image is generated, the photographing field angle information is recorded in an image file with the distance image. In many cases, however, values recorded in image files are rounded to nominal values. Consequently, such values are not suitable for use with image processing that requires high accuracy. Therefore, it is an object of the present invention to provide an apparatus capable of accurately calculating a photographing field angle using a distance image where an approximate value is known but accuracy thereof is not sufficient.